The invention relates generally to vehicle throttle control and, more particularly, to a method and apparatus for controlling vehicle traction on slippery surfaces through throttle variation. Longitudinal vehicle acceleration is controlled by adapting parameters online, with the controller operating to vary feedback gains online based on input/output relationships.
Currently, throttle control systems generally control vehicle acceleration by using fixed parameters online to vary engine throttle and to thereby maximize traction. For example, U.S. Pat. No. 4,843,552 issued to Inagaki discloses a wheel slip control system which controls the rotation of drive wheels to increase the frictional force between the drive wheels and the road surface. The rotation of the drive wheels is controlled by regulating the output power of an internal combustion engine. The difference between the drive wheel speed and the follower speed is used to determine the occurrence of slip.
Another throttle control system is disclosed in U.S. Pat. No. 4,768,608 issued to Hrovat. The Hrovat patent discloses an antislip control method and system for controlling the wheel slip of a vehicle having at least one driven wheel coupled to an internal combustion engine. The control system is basically a simple feedback system having three feedback gains which are fixed. Finally, U.S. Pat. No. 4,771,848 issued to Namba et al discloses a vehicle acceleration control system for controlling traction. The system prevents or limits the slip of vehicle wheels to enable a smooth start and to maximize acceleration. The Namba et al system has fixed gains which are not adaptable. It is seen then that there is a need for a vehicle traction controller in which the traction control, rather than being fixed, is capable of adapting to changes in vehicle and engine parameters in order to compensate for uncertainties in vehicle parameters.